Compressed and thermostated air regulated gas liquid chromatography oven with simultaneously operated multiple chromatography columns

ABSTRACT

The apparatus of the present invention comprises a multiple column gas liquid chromatographic, GLC, oven assymbly for chromatographing a plurality of samples simultaneously. Each of a plurality of GLC columns is contained in a separate small oven whose temperature is independently regulated using a controled flow of compressed and thermostated dry air. Segments of the effluent gas from each of a plurality of GLC columns is passed individually and sequentially to a single detector using a single valve with multiple symmetrically spaced inlets but only two outlets. The effluent gas from all of the GLC columns but one is passed to waste while the effluent gas from one GLC column is passed to a common detector. The valve is repositioned to sequentially pass the effluent gas from each of a plurality of GLC columns to a single detector. The use of a single small valve is made possible by the use of a plurality of micro ovens for individual temperature control of each of a plurality of GLC columns. The use of micro ovens is made possible by the use of compressed and thermostated air as a source of heat for each GLC column oven. This simultaneous operation of a plurality of GLC columns results in a significant increase in the rate of GLC analysis for a plurality of samples.

[451 Get. is, 1974 States Patet n91 McCabe 1 COMPRESSED AND THERMOSTATEDAIIR multiple column gas liquid chromatographic, GLC,

REGULATED GAS LlQUlD oven assymbly for chromatographing a plurality ofCHROMATOQRMJHY ()VEN WITH samples simultaneously. Each of a plurality ofGLC SIMULTANEOUSLY OPERATED MULTIPLE columns is contained in a separatesmall oven whose CHROMATOGRAPHY COLUMNS temperature is independentlyregulated using a con 0 troled flow of compressed and thermostated dryair.

[ lflvenlori William a 2535 3151 Segments of the effluent gas from eachof a plurality E, Wlchlla, Kans- 67217 of GLC columns is passedindividually and sequen- [22] Filed; Sept 25 1972 tially to a singledetector using a single valve with multiple symmetrically spaced inletsbut only two outlets.

[ pp 292,146 The effluent gas from all of the GLC columns but one ispassed to waste while the effluent gas from one GLC column is passed toa common detector. The

[52] U5. 55/197, 55/386 [51] Int.

valve is repositioned to sequentially pass the effluent gas from each ofa plurality of GLC columns to a sin- Btlld 15/08 [58] Field ofSearch......... 210/31 C, 198 C; 55/197,

55/67 386 gle detector. The use of a single small valve is made possibleby the use of a plurality of micro ovens for individual temperaturecontrol of each of a plurality of GLC columns. The use of micro ovens ismade possi- References Cited UNITED STATES PATENTS ble by the use ofcompressed and thermostated air as a source of heat for each GLC columnoven. This simultaneous operation of a plurality of GLC columns resultsin a significant increase in the rate of GLC analysis for a plurality ofsamples.

WM m." mm HM d m w mm w m uk mb BPTF Primary Examiner-John Adee [57]ABSTRACT The apparatus of the present invention comprises a 11 Claims, 4Drawing Figures 3341 ;osa

PATENTEUnm 15 m4 SHEET 1 BF 3 TEMPERATURE is 1|||l| I E II I RCOMPRESSED 0Q 1 riW\ TEMPERATURE v SENSING PRoBEr 2 mmmmsm v 3.841.059

SBEEI 20$ 3 AIR TO OVEN 2| THERMOSTATED COMPRESSED AIR TO TEMPERTURESENSING PROBE l8 v TRANSMISSION HI 5O 49 58'- MOTOR' I RELAY 6| POWER 60SOURCE PATENIEB I FIG.3

SHEEI 3 0F 3 FIG.4

TO EXHAUST DETECTOR COMPRESSED AND THERMOSTATED AIR REGULATED GAS LIQUIDCHROMATOGRAPHY OVEN WITH SIMULTANEOUSLY OPERATED MULTIPLE CHROMATOGRAPHYCOLUMNS BACKGROUND OF THE INVENTION In any forced air oven system thecritical parameters important for temperature regulation of the sametype. They are: (l) the amount of heat absorbed by the oven itself andthe material being heated inside the oven, (2) the heat lost from theoven due to imperfect oven insulation, (3) the temperature of the aircirculated in the oven, and (4) the rate of flow of thermostated air inor through the oven. Most oven systems rely on changes in parameter (3),air temperature, for regulation of oven temperature. In this type ofoven system parameters (I), (2), and (4) are held essentially constant.The system for oven temperature regulation contained in the presentinvention uses an entirely different principle. It maintains parameters(1), (2), and (3) essentially constant and varies parameter (4), therate of flow of thermostated dry air through the oven. This air flowregulation is attained using a separately maintained source ofcompressed and thermostated dry air with a partially manually andpartially automatically operated variable gas flow valve for each of aplurality of GLC column ovens. By using compressed and thermostated airand an air flow regulator valve it is possible to reduce the size ofeach of a plurality of GLC column ovens considerably, which greatlyreduces heat loss due to parameter (1). With these micro ovens aplurality of them can be maintained individually in a very small spaceallowing the use of a single valve for regulating the flow of eachcolumn effluent gas to a common detector. In fact, the multiple columneffluent gas micro regulating valve, contained in the presentinvention,cannot be used effectively without the micro GLC column ovens, which inturn requires the use of compressed air for temperature regulation.

Gas liquid chromatography has been established as a superior means fordoing an almost limitless number of difficult organic analyses. The ovensystems which are presently available, however, do not allow analyticresults to be obtained at a practical rate; in some cases it might takeup to two hours for a single analysis. This usual slow rate of operationhas greatly restricted the use of GLC in the routine analyticallaboratory and has tended to exclude it almost entirely from theclinical chemistry analytical lab where their volume of work isrelatively large and most of the results are needed quickly. The ovensystem described in the present invention allows a plurality of GLCanalyses to be run simultaneously and therefore increases the rate ofanalysis by an order of magnitude over other types of oven systems. Thisstriking increase in rate of analysis which is attained with the presentinvention represents a significant innovation in GLC column oven design.In the case of most routine GLC analyses, only one or a small number ofcomponents in a mixture is important in the analysis. The majority ofthe components in a sample are not important and therefore most of theeffluent gas from a GLC column need not be passed toa detector forquantitation. For a given sample analysis, there are usually componentscoming off the GLC column before and after the component or componentsof interest which could be excluded from the detector and, therefore,from quantitation. All of the present oven systems for GLC analysis mustquantitate all components in a given sample and the time spentquantitating compo nents which are not important in the analysisrepresents a significant increase in the overall time of analysis foreach sample and therefore a striking decrease in the rate of sampleanalysis for a given GLC instrument. The apparatus of the presentinvention is designed to eliminate this unnecessary increase inanalytical time. In the case of the present invention only thosecomponents of a sample which are important for the analysis are passedto the detector for quantitation while most of the other components arepassed to waste. Because the number of components quantitated is smallcompared to the total number of components in the sample being analyzed,there is a tremendous savings in analytical time and therefore anincrease in the rate of analysis by almost an order of magnitude formost samples analyzed.

SUMMARY OF THE INVENTION An object of the present invention is toincrease the rate of gas liquid chromatography, GLC, analysis by thesimultaneous operation of a plurality of GLC columns.

Another object of the present invention is to run a plurality of GLCanalyses simultaneously using only a single detector system by means ofa single micro valve which passes a segment of the effluent gas fromeach of a plurality of GLC columnsindividually and sequentially to thedetector.

Another object of the present invention is to use a plurality of microGLC column ovens, each individually thermostated for constanttemperature operation and/or variable temperature operation, in a smallspace to enable a single micro valve with multiple symmetrically spacedinlets and outlets to either the detector or to waste to be used tosequentially pass a segment of the effluent gas from each of a pluralityof GLC columnsto a single detector.

Another object of the present invention is to use compressed'andthermostated dry air for regulating the oven temperature for each of aplurality of micro GLC column ovens with limited free space for airentrance and circulation.

Another object of the present invention is to provide a plurality ofmicro GLC column ovens with a common source of compressed andthermostated dry air using a compressed air source with its outlet sideattached to a metal tank with interposed moisture trap and appropriatepressure valves to maintain a constant, but adjustable, tank pressure, ametal tank built to withstand the necessary operating temperature andpressure of the dry air and containing a heating means a cooling means,a temperature sensing probe, inlet for dry air from the compressed airsource and outlets for each of the micro GLC column ovens.

Another object of the present invention is to provide a temperatureregulator means for the compressed air tank. which will function to openor close the electric circuit to either the heating or cooling meansdepending on the preset temperature and the temperature inside thecompressed air tank as indicated by a temperature sensing probe.

Another object of the present invention is to provide each micro GLCoven with a partially manually operated and partially automaticallyoperated gas flow regulator valve to control the flow of compressed andthermostated dry air into each of a plurality of GLC column micro ovens.

Another object of the present invention is to provide each micro GLCcolumn oven gas flow regulator valve with a reversible motor and geardrive means to regulate the rate at which the valve is opened or closedwhich determines the rate of flow of thermostated dry air into each GLCcolumn oven which, in turn, determines the temperature inside each oven.

Another object of the present invention is to provide each micro GLCcolumn oven with a temperature regulator means which comprises a settemperature indicator associated with a motor-gear drive means to enablethe set temperature to be altered at variable rates, degrees per minute,a temperature sensing probe inside each GLC column oven, a GLC columnoven temperature indicator, and a means to reverse the current to theair flow regulator reversible drive motor depending on whether the GLCcolumn oven temperature is less or greater than the set temperature.

Another object of the present invention is to place the GLC column microoven temperature sensing probe for each oven in contact with the GLCcolumn effluent gas.

Another object of the present invention is to provide each GLC columnmicro oven gas flow valve motorgear means with a mechanical stop toprevent the valve from being opened past a preset point and thus preventthe oven from being heated beyond a given final temperature.

Another object of the present invention is to provide a means forpreheating the carrier gas for each GLC column inside the GLC columnmicro oven before the carrier gas inters the GLC column.

Other objects and further scope of applicability of the presentinvention will become apparent from the detailed description givenhereinafter; it should be understood, however, that the detaileddescription and specific examples, while indicating preferredembodiments of the invention, are given by way of illustration only,since various changes and modifications within the spirit and scope ofthe invention will become appar ent to those skilled in the art fromthis detailed description.

The general, overall operation of the apparatus of the present inventioncan be defined as follows. The gas flow regulator valves to the GLCcolumn micro ovens are closed manually. The appropriate compressed airtank pressure is set on the tank pressure gauge and the pressure releasegauge is set slightly higher than the tank pressure. The conduit meansbetween the compressed air source and the tank is opened. The compressedair tank temperature regulator is set to heat or cool as required. Theproper compressed air tank operating temperature is set on thethermostat and the switch connecting the compressed air tank temperatureregulator to line voltage is turned on. As soon as the compressed airtank has reached the proper operating temperature and pressure, theautomated drive means for each air flow regulator valve is disengagedand each GLC column oven gas flow regulator valve is manually opened aslight amount. The column effluent gas valve is set to pass the effluentgas from column one to the detector and the carrier gas valve for eachGLC column is opened and its proper flow rate is set. Each air flowregulator valve is opened manually until the proper final oventemperature is maintained by each oven as indicated by the temperatureindicator means for each GLC column micro oven. The mechanical stop pinsfor each flow regulator valve automated opening drive means are now set.The mechanical stop pin is placed into the proper hole of the mechanicalstop drive wheel to force the air flow regulator valve drive gear meansto disengage when this amount of rotation of the mechanical stop drivewheel has occurred. Now each flow valve is manually closed until thetemperature for each GLC column oven holds at the proper initialoperating temperature. A second pin is placed in the mechanical stopwheel of each air flow regulator valve drive means to mark this positionfor subsequent resetting. The set temperature indicator on each GLCcolumn oven temperature programming thermostat is disengaged and movedto indicate the initial operating temperature and a mechanical stop ispositioned at a position equivalent to the final operating temperature.The set temperature indicator on the temperature programming thermostatwill then stop when it reaches the final operating temperature setting.The means for manually disengaging the automated drive assymbly for eachair fiow regulator valve is released. The variable speed gear box forboth the air flow regulator valve drive means and the temperatureprogramming drive means for each GLC column oven are set for the properrate of temperature rise. Now each GLC column oven variable temperatureprogramming means and sample injection will be started in a delayedsequence. The line voltage switch for the GLC column oven temperatureprogramming means for column one will be turned on and a sample injectedinto column one, then after a given time interval the switch for columntwo will be turned on and a sample injected into column two and theprocedure continued until all columns have been started. As soon as thatportion of the component peaks separated by column one which are to bequantitated start reaching the detector the time interval for injectionof samples is repeated for timing the turning of the GLC column effluentgas valve from column one to column two and so forth until a segment ofthe effluent gas from each GLC column has been quantitated.

To convert from variable temperature operation to constant temperatureoperation just set each temperature programming variable speed gear boxto zero rate of change and repeat the remaining steps listed above.

The partially manual and partially electronic means of regulating therate of opening of each air flow regulator valve described in thepresent invention is just one of many possible means, some being totallyautomated, for regulating the rate of opening of an air flow regulatorvalve to achieve a programmed variable temperature operation of a GLCcolumn oven. Substitution of any one of the other possible means wouldnot change the basic principle of GLC column oven temperature regulationwhich depends on the control of the flow of compressed and thermostatedgas, air in this case, into an oven, a micro oven in this case,described in the present invention.

There are a number of different means of obtaining and/or maintainingcompressed and thermostated gas for regulating the temperature of a GLCcolumn oven, but none of these alternate means would constitute a changein the basic principle of using compressed and thermostated gas to heata GLC column oven as described in the present invention.

There are a number of different valve designs similar to the GLC columneffluent gas valve described as part of the present invention but noneof these would alter the basic principle of a plurality of GLC columneffluent gas inlets and outlets to either waste or the detector and withthe capability of sequentially passing a small segment of the total gaseffluent from each of a plurality ,of columns to a single detector asdescribed in the present invention.

The drawings and descriptions presented hereinafter and above whichspecify a given GLC column micro oven system with a set number of GLCcolumn micro ovens is presented simply to illustrate the basic charac-'teristics of the present invention. Certainly any number of micro ovenscould be used in actual practice and would only constitute additionalembodiments of the apparatus described in the present invention.

There are a variety of analytic modes of operation for the GLC ovenassymbly described in the present invention but in all cases the basicprinciple is the same. Only that portion of the effluent gas from eachof a plurality of GLC columns which is important in the analysis of asample is passed to the detector for final quantitation. By operating aplurality of columns essentially simultaneously one is able to reducethe time of analysis for any GLC column system, reguardless of total runtime for a given sample on the column, to just that segment of timenecessary to quantitate the component or components of interest. Withthis GLC oven system, except for the first and last GLC columns, one nolonger needs to wait for components running before or after thatcomponent to be quantitated to clear the detector. One simply passes theeffluent gas from each of a plurality of columns to the detector onlywhen a component or components of interest is coming off the columns.This column effluent valving system has no direct affect on theseparation of components of a sample on the GLC column and also has noaffect on the detector operation. The valving system illiminates timespent quantitating those components which are of little or no interestin the analysis of a sample. With this valving system, the effectivetime of GLC analysis for each sample is reduced by an order of magnitudein most cases. The column effluent valving assymbly described in thepresent invention is a means for increasing the rate of analysis but hasno significant qualitative affect on the gas liquid chromatographicanalysis of a sample.

DESCRIPTION OF THE DRAWINGS The present invention will become more fullyunderstood from the detailed description given hereinbelow and theaccompanying drawings which are given by way of illustration only andthus are not limitative of the present invention and wherein,

FIG. 1 shows a schematic representation of the invention with the ovenassymbly in exploded perspective;

FIG. 2 shows a schematic diagram of the oven temperature programmingmeans;

FIG. 3 shows an exploded perspective view of the GLC column effluent gasvalve assymbly; and

FIG. 4 shows a longitudinal section view of the GLC column effluent gasvalve assymbly of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The gas liquid chromatography,GLC, column oven apparatus of the present invention according to FIG. 1comprises a GLC column effluent gas valve assembly I which includes afemale valve seat 2 containing a plurality of inlet holes 3symmetrically spaced around the valve seat. Each of the inlet holes 3are connected by appropriate conduit means 4 to the outlet side of oneof a plurality of GLC columns 5. The effluent gas from each GLC columnpasses through a conduit means 4 and into the valve at one of the inletholes 3. The efflu ent gas from one of a plurality of columns is passedto the bottom of the valve assymbly and out the detector outlet hole 6.The effluent gas from the remainder of the GLC columns passes throughthe inlet holes in the wall of the female valve seat and throughmatching holes in the wall of the male valve seat 7 to the hollow centerof the male valve seat and up through the hollow rod S to waste. Themale. valve seat 7 can be rotated around rod 8 as its axis tosequentially pass a segment of the effluent gas from each of a pluralityof GLC columns through the detector outlet 6 to a single detector meansnot shown in the drawings. The GLC column effluent gas valve assymbly 1is contained within an insulated chamber comprising a top piece 9, amiddle piece It), and a bottom piece Ill. The bottom piece 11 of thevalve chamber has an outlet 12 in the bottom for the conduit meansconnecting the valve detector outlet 6 with the detector. The middlepiece 10 of the valve chamber has a plurality of flanges 13symmetrically spaced around the chamber for attachment of an equalnumber of GLC column assymblies 14. Each GLC column assymbly 14comprises a length of carrier gas conduit tubing 15 which is connectedat one end to a source of compressed carrier gas, not shown in thedrawings, and at the other end to a standard combined carrier gas-sampleinlet means 16. The carrier gas conduit tubing 15 is folded to fill thespace between the inlet and outlet sides of the GLC column 5 to preheatthe carrier gas before it inters the GLC column. Each GLC column 5 isconnected to the valve chamber middle piece flange 13 at the carrier gasinlet side by means of the standard combined carrier gas-sample inletmeans 16 and at the effluent gas outlet side by standard tube fittingmeans 117. The GLC column micro oven temperature sensing probe 18 isattached inside tube fitting means 17 to monitor the temperature of theGLC column effluent gas. The hot oven air in the vicinity of the foldedcarrier gas conduit tubing 15 and GLC column 5 passes from the GLCcolumn micro oven through the small orifice l9 and into the valvechamber. There is an exhaust outlet 20 for the hot air in the bottom ofthe valve chamber bottom piece 11. The path of the hot air is indicatedby the arrows. The circulation of hot air from each of the GLC columnmicro ovens through the valve chamber serves to maintain the valveassymbly 1 at approximately the average temperature of the plurality ofGLC column micro ovens. Each of the GLC columns 5 and its carrier gasconduit tubing 15 vfts inside a GLC column micro oven 21. Each oven 21is attached by suitable conduit means to a common tank 22 of compressedand thermostated air through an air flow regulator valve 23. The airpressure inside tank 22 is maintained by a source of compressed air 24and a pressure regulator valve 25 and a pressure release valve 26. Thetemperature of the air in tank 22 is maintained by a temperatureregulating means comprising a heating means 27, a cooling means 28, atemperature sensing probe 29, and a thermostat 30. The temperaturesensing probe 29 and thermostat 30 are connected by suitable electricalmeans 31. Each air flow regulator valve 23 can be controled manuallyusing knob 32 or automatically by means shown in FIG. 2. The temperatureinside each of a plurality of micro ovens 21 is controled by the amountof thermostated air flowing into each oven through one of a plurality ofair flow regulator valves 23.

FIG. 2 shows a schematic illustration of one of a plurality of automaticmeans for controling each of the air flow regulator valves 23 associatedwith each of a plurality of GLC column micro ovens 21. It comprises aclutch assymbly 33, a variable speed motor-gear drive means 34, and atemperature programming means 35. The clutch assymbly 33 is associatedwith the air flow regulator valve 23 by suitable gear means 36 and tothe motor-gear drive means 34 by drive gear 37. Clutch assymbly 33comprises a primary drive gear means 38 which is held in contact withgear means 36 by rod 39 and spring 40. Gear means 38 can be disengagedmanually from gear means 36 by pulling out rod 39 and moving pin 41 tothe forward hole shown in rod 39. In this position the air flowregulator valve 23 can be operated manually using knob 32. Gear means 38drives gear means 36 which drives the air flow regulator valve 23 openor closed and also turns gear 42. Gear 42 is attached to wheel 43 whichturns as gear 42 turns. Wheel 43 has a plurality of pin holes evenlyspaced around its circumference. Pins 44 can be placed in wheel 43 andthese pins will contact rod 39 whenever wheel 43 has rotated into theproper position as shown in FIG. 2. Whenever pin 44 contacts rod 39 itpushes both rod 39 and the attached gear means 38 back against spring 40which causes gear means 38 and 36 to disengage and thus stops theautomatic opening of the air flow regulator valve 23. By placing pin 44in the proper hole in wheel 43 the automatic opening of the air flowregulator valve 23 can be stopped at any point between fully closed andfully open. The variable speed motor-gear drive means 34 comprises areversible motor 45 which drives gear 37 through a variable speed gearbox 46. The rate of rotation of drive gear 37 can be varied by changinggears in gear box 46. Different rates of rotation of gear 37 representdifferent rates of opening of the air flow regulator valve 23corresponding, approximately, to different rates of rise of temperaturein the corresponding GLC column micro oven 21. The direction motor 45turns and therefore whether the air flow regulator valve 23 is beingopened or closed is controled by the temperature programming means 35which comprises a relay 47 connected to motor 45 by means 48 and tothermostat 49 by means 50. Thermostat 49 has a temperature indicator 51associated with the GLC column micro oven temperature sensing probe 18by means 52 and a set temperature indicator 53 which can be set manuallyor driven automatically by gear 54, belt drive 55, gear 56, variablespeed gear box 57, and motor 58. Relay 47 and motor 58 are connected toa power source by electrical means 59 and 60 through switch 61. Theposition of the set temperature indicator 53 can be varied automaticallyfrom some manually set initial temperature to a predetermined finaltemperature setting by rotation of the gear means 55, 56, and 57. Therate of change of the set temperature indicator setting in degrees perminute is determined by the arrangement of gears in the variable speedgear box 57 which determines the rate of rotation of gear 56. When thetemperature indicator 51 is at a lower temperature than the settemperature indicator 53 the current from relay 47 to reversible motor45 is such that the air flow regulator valve 23 is driven open. Whenindicator 51 is at a higher temperature than indicator 53 the currentfrom relay 47 is reversed and motor 45 drives the air flow regulatorvalve 23 closed.

FIGS. 3 and 4 show an exploded perspective view and a longitudinalsection view of the GLC column effluent gas valve assymbly. FIG. 3comprises a lever 62 which can be rotated in a vertical plane to seatand unseat the valve or in a horizontal plane to reposition the malevalve seat to sequentially pass a segment of the effluent gas from eachof a plurality of GLC columns to a single detector. Lever 62 is attachedby pin 63 to hollow rod 8 which serves both as a means for repositioningthe male valve seat 7 which includes wall 64 and as a waste gas conduitmeans from the valve assymbly. The effluent gas from all but one of theGLC columns is passed to waste through hollow rod 8. The male and femalehalves of the valve seat are forced together by spring 65 pressingagainst spring support 66 which is attached to rod 8. Rod 8 is held inproper vertical position by guide 67 which is attached to the top flange68 of the female portion of the valve seat 2. The top flange 68 of thefemale valve seat 2 has a plurality of GLC column effluent gas inletholes 69 symmetrically spaced around the valve seat and an outlet 70,shown in FIG. 4, to the detector at the bottom. The wall 64 of the malevalve seat 7 also has a plurality of GLC column effluent gas inlet holes71 symmetrically spaced around the valve seat with one replaced by anarrow grove 72 on the outside which connects one of the inlet holes 69in the female valve seat 2 to the detector outlet hole 70. The inletholes 69 and 71 in the female and male valve seats are spaced so theyexactly match. The effluent gas from all of the GLC columns but one passto the center of the valve assymbly through holes 69 and 71 in thefemale and male valve seat walls and on to waste through the hollow rod8.

FIG. 4 shows the two alternate paths for the GLC col umn effluent gas asindicated by the arrows. For the effluent gas from the GLC column beingpassed to the detector, the effluent gas inters the female valve seat 2through inlet 74 and hole 69 in flange 68, passes to the bottom of thevalve assymbly down grove 72 between walls 64 and 73 along path 75 asindicated by the arrows. It passes through hole in the bottom of thevalve assymbly and out of the bottom of the female valve seat 2 throughthe detector outlet 6 along path 76 as indicated by the arrow. Theefiluent gas from each of the remaining GLC columns is passed by similarroutes to waste. The effluent gas from this plurality of columns intersthe female valve seat 2 through a plurality of inlets 77, passes to thecenter of the valve assymbly through a matching set of inlet holes 71 inthe wall 64 of the male valve seat 7 and along path 78 as indicated bythe arrows up through the hollow rod 8 to waste along path 79 indicatedby the'arrow. Rod 8 is held in a vertical position by guide 67 which isattached to the female valve seat 2.

I claim: 1. An apparatus for performing simultaneous gas liquidchromatographic analyses on a plurality of samples comprising aplurality of micro ovens, a chromatogra- 7 carrier gas, a segment ofconduit means for said carrier gas contained in each of said ovens andconnected to the inlet of each of said chromatography columns; a valveassymbly contained in an insulated chamber hav ing an aperature to eachof said ovens, said valve assymbly having a plurality of inletsconnected by conduit means to the outlet of each of said columns, saidvalve means containing passage means sequentially connecting one of saidcolumns to a detector means and the other of said columns to a wasteoutlet means; a chromatography column micro oven, compressed air heatingmeans comprising a tank for holding compressed and thermostated air witha plurality of outlets each connected to one of said ovens, an airtemperature and pressure regulating means for said compressed air tankand a plurality of air flow regulating means in the said connectionsbetween said tank and each of said ovens.

2. The apparatus of claim ll, wherein the segment of conduit means forsaid carrier gas comprises a length of folded carrier gas conduit tubinglocated inside each chromatography column micro oven and connected tothe inlet of each chromatography column.

3. The apparatus of claim 2, wherein the length of folded carrier gasconduit tubing located inside each chromatography column micro ovenserves to preheat said carrier gas to the temperature of the said microoven prior to said carrier gas entering said chromatography column.

4. The apparatus of claim 1, wherein the micro ovens are each just largeenough to contain one chromatogra' phy column, a length of foldedcarrier gas tubing and just sufficient free space for circulation ofcompressed and thermostated air.

5. The apparatus of claim 1, wherein the valve assymbly having aplurality of inlets connected by conduit means to the outlet of each ofsaid columns is adjustable to pass a portion of the column effluentcarrier gas from each of a plurality of chromatography columnssequentially to a detector means while passing the effluent carrier gasfrom all other said columns to waste.

6. The apparatus of claim ll, wherein the insulated chamber for the saidcolumn effluent gas valve assymbly contains conduit means forcirculation of said compressed and thermostated air around said valveassymbly comprising an aperature to each of said micro ovens and asingle exhaust outlet.

7. The apparatus of claim 1, wherein the air temperature and pressureregulating means for said compressed air tank comprises a temperaturesensing probe, a heating means, a cooling means, a temperature regulatormeans and an inlet from a compressed air source.

8. The apparatus of claim 7, wherein the inlet from a compressed airsource contains a pressure regulating means which functions to open orclose said inlet depending on the pressure inside said compressed andthermostated air tank and the pressure set on said pres sure regulatingmeans.

9. The apparatus of claim 1, wherein the air flow reg ulating meansbetween said tank and each of said ovens comprises an air flow regulatorvalve, a motor-gear drive means to automatically open and close the saidair flow regulator valve at one of several preset rates, eachcorresponding to a different rate of temperature increase inside saidchromatography column micro oven, a mechanical stop means to disengagethe said automatic motor-gear drive means from the said air .flowregulator valve and a separate electrical feedback means to reverse themotor of each said air flow regulator valve motor-gear drive meansdepending on whether the temperature of the chromatography column isless or greater than the temperature set on a chromatography columntemperature regulator means.

10. The apparatus of claim 9, wherein the electrical feedback means foreach said air flow regulator valve motorgear drive means comprises amotor-gear drive means which functions to vary a thermostat set temperature at various preset rates, a chromatography column than the saidthermostat means set temperature.

1. An apparatus for performing simultaneous gas liquid chromatographicanalyses on a plurality of samples comprising a plurality of microovens, a chromatography column contained in each of said ovens, saidcolumns having an inlet and outlet means, said inlet having separateconduit means for sample and carrier gas, said outlet having a singleconduit means for sample and carrier gas, a segment of conduit means forsaid carrier gas contained in each of said ovens and connected to theinlet of each of said chromatography columns; a valve assymbly containedin an insulated chamber having an aperature to each of said ovens, saidvalve assymbly having a plurality of inlets connected by conduit meansto the outlet of each of said columns, said valve means containingpassage means sequentially connecting one of said columns to a detectormeans and the other of said columns to a waste outlet means; achromatography column micro oven, compressed air heating meanscomprising a tank for holding compressed and thermostated air with aplurality of outlets each connected to one of said ovens, an airtemperature and pressure regulating means for said compressed air tankand a plurality of air flow regulating means in the said connectionsbetween said tank and each of said ovens.
 2. The apparatus of claim 1,wherein the segment of conduit means for said carrier gas comprises alength of folded carrier gas conduit tubing located inside eachchromatography column micro oven and connected to the inlet of eachchromatography column.
 3. The apparatus of claim 2, wherein the lengthof folded carrier gas conduit tubing located inside each chromatographycolumn micro oven serves to preheat said carrier gas to the temperatureof the said micro oven prior to said carrier gas entering saidchromatography column.
 4. The apparatus of claim 1, wherein the microovens are each just large enough to contain one chromatography column, alength of folded carrier gas tubing and just sufficient free space forcirculation of compressed and thermostated air.
 5. The apparatus ofclaim 1, wherein the valve assymbly having a plurality of inletsconnected by conduit means to the outlet of each of said columns isadjustable to pass a portion of the column effluent carrier gas fromeach of a plurality of chromatography columns sequentially to a detectormeans while passing the effluent carrier gas from all other said columnsto waste.
 6. The apparatus of claim 1, wherein the insulated chamber forthe said column effluent gas valve assymbly contains conduit means forcirculation of said compressed and thermostated air around said valveassymbly comprising an aperature to each of said micro ovens and asingle exhaust outlet.
 7. The apparatus of claim 1, wherein the airtemperature and pressure rEgulating means for said compressed air tankcomprises a temperature sensing probe, a heating means, a cooling means,a temperature regulator means and an inlet from a compressed air source.8. The apparatus of claim 7, wherein the inlet from a compressed airsource contains a pressure regulating means which functions to open orclose said inlet depending on the pressure inside said compressed andthermostated air tank and the pressure set on said pressure regulatingmeans.
 9. The apparatus of claim 1, wherein the air flow regulatingmeans between said tank and each of said ovens comprises an air flowregulator valve, a motor-gear drive means to automatically open andclose the said air flow regulator valve at one of several preset rates,each corresponding to a different rate of temperature increase insidesaid chromatography column micro oven, a mechanical stop means todisengage the said automatic motor-gear drive means from the said airflow regulator valve and a separate electrical feedback means to reversethe motor of each said air flow regulator valve motor-gear drive meansdepending on whether the temperature of the chromatography column isless or greater than the temperature set on a chromatography columntemperature regulator means.
 10. The apparatus of claim 9, wherein theelectrical feedback means for each said air flow regulator valvemotor-gear drive means comprises a motor-gear drive means whichfunctions to vary a thermostat set temperature at various preset rates,a chromatography column temperature sensing probe connected by suitableconduit means to said thermostat, a suitable conduit means between saidthermostat means and said air flow regulator valve drive motor, asuitable relay means contained in said conduit means between saidthermostat means and said valve drive motor.
 11. The apparatus of claim10, wherein the suitable relay means functions to reverse the electricalcurrent to the said air flow regulator valve drive motor depending onwhether the temperature of the effluent carrier gas from saidchromatography column is greater or less than the said thermostat meansset temperature.